As is known, the industrial bottling plants which are commercially available today usually use several operating machines arranged in series in order to perform the operations of rinsing, filling, corking/capping, labelling, etc.
For this purpose, the abovementioned operating machines have mounted peripherally, on a turntable, a plurality of operating heads with which the containers are associated, along their travel path around the turntable, in order to undergo the operations to be performed by the operating machine.
Transfer of the containers between the various operating machines, namely around the turntables of the said operating machines, is performed using conveying means such as screw feeders, motor-driven recessed starwheels, retaining grippers and conveyor belts.
There is a particularly pressing need in the sector to ensure versatile operation of the bottling plants using containers of varying shapes and sizes. For this purpose, the conveying means are currently adapted so as to retain correctly the containers, by replacing the screw feeders or the grippers, in particular so as to centre the containers correctly with respect to the heads of the operating machines. In fact, if the containers vary their position on the support base of the turntable when there is a variation in size, it is obvious that they will no longer be aligned with the operating heads of the various machines.
The adaptation which is required whenever there is a production change-over in order to use containers with a different shape obviously results in a considerable amount of time being lost and production downtime due to the plant being out of action, this having a negative effect on the overall production efficiency and therefore costs.
In order to overcome these drawbacks, numerous gripper-type conveying means able to operate with different-size containers have been developed. For example, the patent EP 0366225 describes an apparatus for conveying containers, equipped with a turntable rotating about a central axis of rotation. A plurality of grippers are mounted peripherally on said turntable, each of these grippers comprising a pair of arms which are pivotably mounted on a turntable support disc. The free end of each arm is provided with a projection for facilitating gripping of the containers, while the end connected to the central disc has, keyed thereon, a toothed wheel engaged with the toothed wheel of the other gripper arm. A vertical rod is connected at one end to one of the arms of the grippers and at the other end to a cam mechanism. The latter comprises a frustoconical cam which acts on a cam follower mechanically coupled with the vertical rod by means of lever mechanisms and resilient means. In operational terms, the cam causes a radial displacement of the follower away from or towards the central axis, causing a rotation of the vertical rod which, in turn, causes opening or closing of the gripper arms. This conveying apparatus also comprises a control device for adjusting the closing and opening angle of the grippers so as to allow the latter to retain containers which have a base of varying diameter. This control device comprises a gear-type raising mechanism which allows lowering or raising of the frustoconical cam so as to keep the cam follower more or less close to the central axis during the entire rotation of the turntable so as to reduce or increase the maximum closing or opening angle of the grippers.
This solution, however, in practice also has a number of drawbacks.
A first drawback consists in the fact that the grippers of this apparatus are intended to convey only containers with a circular base, but are unable to retain and centre correctly containers with other shapes commonly found in the market, such as bottles with a square, rectangular or triangular base.
A further drawback consists in the fact that adjustment operations are nevertheless required in order to adapt the grippers so that they can retain containers with different diameters. These operations require stoppage of the entire bottling plant with consequent production downtime and reduced efficiency of the production process.
Moreover, adjustment of the grippers, by means of the control device employed in the conveying apparatus described briefly above, does not solve entirely the problem of radial displacement of the containers when there is a variation in their shape and size, with the consequent risk of misalignment between the mouth of the containers and the heads of the operating machines.
Another drawback is associated with the high constructional complexity of the apparatus for conveying containers of the known type, which may give rise to faults or malfunctions.